You can use ~ like {{ foo ~ 'inline string' ~ bar.fieldName }}
But you can also create your own concat function to use it like in your question:
{{ concat('http://', app.request.host) }}:
In src/AppBundle/Twig/AppExtension.php
<?php
namespace AppBundle\Twig;
class AppExtension extends \Twig_Extension
{
/**
* {@inheritdoc}
*/
public function getFunctions()
{
return [
new \Twig_SimpleFunction('concat', [$this, 'concat'], ['is_safe' => ['html']]),
];
}
public function concat()
{
return implode('', func_get_args())
}
/**
* {@inheritdoc}
*/
public function getName()
{
return 'app_extension';
}
}
In app/config/services.yml:
services:
app.twig_extension:
class: AppBundle\Twig\AppExtension
public: false
tags:
- { name: twig.extension }